Student Article

Bioluminescence — the ability of living organisms to produce light — is one of nature’s most captivating adaptations.

Glow in the dark? That’s a real thing!

Though most commonly associated with glow-worms and fireflies, bioluminescence is widespread, appearing in marine animals like jellyfish and squid, insects, fungi, crustaceans, and even a 6-foot-long Australian earthworm named Terriswalkeris terraereginae. Notably, the only major groups that lack glowing members are flowering plants and land-dwelling vertebrates.

The science behind the shine

This phenomenon depends on a light-producing chemical reaction involving a molecule called luciferin, which emits light when it oxidizes. In contrast to typical combustion, almost all the energy is released as light rather than heat. The enzyme luciferase acts as a catalyst in this reaction, and slight variations in luciferase explain why glow-worms emit green light, while fireflies may glow yellow despite using the same luciferin.

Why the ocean glows blue

In marine environments, the blue glow common among creatures comes from coelenterazine, a widespread luciferin compound. Some organisms don’t generate light themselves but rely on bioluminescent bacteria, often housed in specialized light organs called photophores, which include lenses, reflectors, and shutters to direct the light.

Lights with a purpose

Glow-worms serve as an example of how bioluminescence serves both reproductive and defensive functions. Flightless females glow to attract flying males, while their larvae flash to warn predators of their toxicity.

Bugs, mushrooms, and sneaky tricks

Meanwhile, fireflies from the Photuris genus take deception to a new level, mimicking the mating signals of other species to lure and consume unsuspecting males. Fungi also glow, sometimes to attract insects that spread spores. In other cases, the light may simply result from chemical waste byproducts.

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